Ferroelectric switching properties of highly c-axis oriented YMnO ₃ gate capacitors

YMnO ₃ (YMO) thin films were deposited on p-Si(100) substrates by radio frequency sputtering. The deposition conditions of oxygen partial pressure and annealing temperature have significant influences on the preferred orientation of YMO film and the size of memory window. The results of X-ray diffraction showed that the film deposited in an oxygen partial pressure of 0% was highly oriented along the c-axis after annealing at 870°C for 1 hr. However, the films deposited in the oxygen partial pressures of 10-20% showed the polycrystalline phase as well as excess Y ₂O ₃ content. Typical memory window of the YMO thin film deposited in 0% O ₂ was 1.24 V at applied voltage of 5 V, which is 5 times wider than that of the film deposited in 20% O ₂ (0.25 V) at the same gate voltage, because the former film was well crystallized along the c-axis.